President Donald Trump on Monday lashed out at former Russian President Dmitry Medvedev for claiming that multiple countries are "ready to directly supply" Iran with nuclear warheads as a result of the U.S. strikes on key Iranian nuclear sites.

"Did he really say that or, is it just a figment of my imagination?" Trump said of Medvedev, the deputy chairman of Russia's security council. "If he did say that, and, if confirmed, please let me know, IMMEDIATELY," he wrote on Truth Social.

Trump chided Medvedev that the "N word" — which he specified stood for "Nuclear" — "should not be treated so casually." But his response included a similar bout of nuclear saber-rattling, suggesting that the president feels emboldened after ordering the bomb attacks against Iran late Saturday Eastern time.

"By the way, if anyone thinks our 'hardware' was great over the weekend, far and away the strongest and best equipment we have, 20 years advanced over the pack, is our Nuclear Submarines," Trump wrote, calling them "the most powerful and lethal weapons ever built."

Trump added, "I guess that's why Putin's 'THE BOSS.'"

The post came in response to Medvedev, who preceded Vladimir Putin as president, criticizing the U.S. strikes on social media while downplaying their impact on Iran, a Russian ally.

While Trump and Defense Secretary Pete Hegseth boasted that the attacks had "obliterated" Iran's nuclear ambitions, the International Atomic Energy Agency said Sunday morning London time that it detected "no increase in off-site radiation levels has been reported as of this time."

Vice President JD Vance in a Sunday interview declined to say that the U.S. is certain that Iran's nuclear sites were destroyed, though he said he believes "we have really pushed their program back by a very long time."

But Medvedev wrote early Sunday morning ET on X that Iranian nuclear infrastructure appears to have sustained only minor damage, and asserted that the "future production of nuclear weapons" will continue.

He added that, "A number of countries are ready to directly supply Iran with their own nuclear warheads" following the U.S. strikes.

Medvedev also mocked Trump for having "pushed the US into another war" that most countries oppose.

"At this rate, Trump can forget about the Nobel Peace Prize — not even with how rigged it has become. What a way to kick things off, Mr. President. Congratulations!"

Russia's current president, Putin, on Monday condemned the U.S. military action as "absolutely unprovoked aggression" and claimed that Moscow is making efforts to aid the Iranian people.